The present invention relates to aircraft tail skid assemblies and more particularly to a high energy absorbing tail skid assembly having a predetermined failure mode.
Crushable energy absorbers are well documented in the prior art as shown for example in U.S. Pat. Nos. 3,130,819; 3,228,492; 3,252,548; 3,265,163; 3,295,798; 3,493,082; and 3,664,463. A crushable energy absorber has been shown in an airplane tail wheel as shown in U.S. Pat. No. 3,130,819. The use of a crushable energy absorber for the purpose of directly protecting an aircraft fuselage is shown in U.S. Pat. No. 3,252,548 and U.S. Pat. No. 3,493,082 shows such use with an airplane tail skid.
In contrast to the aforementioned exemplary prior art, the subject tail skid assembly includes the following: a fuse pin, a fuse link, a pivot link, a drag link and an aluminum crushable cartridge mounted to a telescoping rod assembly.
A tail strike of a magnitude less than the predetermined crush load of the crushable cartridge, has no effect on the tail skid assembly, except possibly a slight wear mark on the tail skid shoe.
In the advent of a tail strike of a magnitude in excess of the designed total capacity of the crushable cartridge the mounting linkage remains rigid, until the load on the fuse pin 27 exceeds its predetermined shear load, at which time the fuse pin 27 will shear thereby precluding damage to the basic aircraft structure 12.
Once the fuse pin 27 has sheared, the pivot link 24 is then free to rotate, which allows the drag link 31 to rotate up until it bottoms out against the stop provided by 34.
The pivot link 24 is designed to rotate up and aft, which prevents damage to the flight control system in the advent of the telescoping rods 22 and crushable cartridge 21 failing to collapse.
Accordingly it is an object of the present invention, to provide a pivotally mounted high energy absorbing aircraft tail skid assembly, which has a predetermined failure mode. It is yet a further object of the present invention, to provide a visual inspection after a tail strike, of the present pivotally mounted high energy absorbing aircraft tail skid assembly, by observation of a metered decal from the ground.